How to POST and GET a model with Foreign Key - django

Question

I am working on a NextJS + Django REST Framework project where I have three models; Document, MySource, and QuestionBlock.
Document is created along with several “question_blocks” linked to the created document. They are created together, and I have already implemented this with nested serializers.
After the Document is created, I want to be able to POST a MySource model linked to the document. Then, when I make a GET request of a document, all mysource objects should be displayed as well.
POST request: notice how I just put the document’s id that I want to link with.
{
"url": "urlasdf",
"title": "tuitle",
"publisher": "afdfas ",
"desc": "qwefqwef",
"summary": "asdfasdf",
"document": "J9DY2pE"
}
GET request: I want the document GET request to show something like below.
"id": "LwpQr6Y",
"question_blocks": [
{
"id": 16,
"document": "LwpQr6Y",
"title": "question 4",
"content": "qweqgadssdffasdf asdf"
},
]
"mysource": [
{
"id": 16,
"url": "google.com",
etc. . .
},
],
"title": "renamed title",
"template": "commonapp",
"updated": "2022-05-19T02:16:00+0000",
"created": "2022-04-21T06:59:05+0000"
The weird part is that I do not see any errors with the code below, and the functionality itself is working properly. But when I attempt to GET the document which has at least one mysource object, it takes at a couple minutes to load, which is making me think there’s something wrong with my code that is perhaps making DRF repeat itself.
models.py
class Document(models.Model):
id = HashidAutoField(primary_key=True)
title = models.CharField(max_length=100, default="Untitled")
template = models.CharField(max_length=100, default="")
updated = models.DateTimeField(auto_now=True)
created = models.DateTimeField(auto_now_add=True)
def __str__(self):
return self.title
class QuestionBlock(models.Model):
id = models.AutoField(primary_key=True)
document = models.ForeignKey(
Document,
related_name="question_blocks",
on_delete=models.CASCADE,
null=True,
blank=True,
)
title = models.CharField(max_length=500, default="")
content = models.CharField(max_length=100000, default="", blank=True)
class MySource(models.Model):
id = models.AutoField(primary_key=True)
document = models.ForeignKey(
Document,
related_name="mysource",
on_delete=models.CASCADE,
null=True,
blank=True,
)
url = models.CharField(max_length=500, default="")
title = models.CharField(max_length=500, default="", blank=True)
publisher = models.CharField(max_length=500, default="", blank=True)
desc = models.CharField(max_length=500, default="", blank=True)
summary = models.CharField(max_length=500, default="", blank=True)
serializers.py
class MySourceSerializer(serializers.ModelSerializer):
class Meta:
model = MySource
fields = ("id", "url", "title", "publisher", "desc", "summary")
def to_representation(self, instance):
self.fields["document"] = DocumentSerializer(read_only=True)
return super(MySourceSerializer, self).to_representation(instance)
class DocumentSerializer(serializers.ModelSerializer):
id = HashidSerializerCharField(source_field="documents.Document.id", read_only=True)
question_blocks = QuestionBlockSerializer(many=True)
mysource = MySourceSerializer(many=True)
class Meta:
model = Document
fields = "__all__"
def create(self, validated_data):
question_blocks = validated_data.pop("question_blocks")
document = Document.objects.create(**validated_data)
for qBlock in question_blocks:
QuestionBlock.objects.create(document=document, **qBlock)
document.save()
return document
EDIT: adding the QuestionBlockSerializer for more context
class QuestionBlockSerializer(serializers.ModelSerializer):
document = serializers.PrimaryKeyRelatedField(
pk_field=HashidSerializerCharField(source_field="documents.Document.id"),
read_only=True,
)
class Meta:
model = QuestionBlock
fields = "__all__"
optional_fields = ["content"]

Answer 1

I think that an appropriate way to do this maybe be this one:
###imports
from django.forms.models import model_to_dict
class DocumentListingField(serializers.RelatedField):
def to_representation(self, instance):
return model_to_dict(instance.document)
and then in MySourceSerializer remove the to_representation function and update to something like this:
class MySourceSerializer(serializers.ModelSerializer):
document = DocumentListingField(many=False, read_only=True)
class Meta:
model = MySource
fields = (
"id", "url", "title", "publisher", "desc", "summary", "document")
*Edit: I added the read_only set to True, 'caus the those models are using Hashfields thar are not easily selializable.
**edit:The reason that cause the slow response it's becaus you have a circle call of serializators so the system never know when to stop.
right here:
class MySourceSerializer(serializers.ModelSerializer):
def to_representation(self, instance):
...
self.fields["document"] = DocumentSerializer(read_only=True)
#Mysource its calling Documentserializer
...
#And here:
class DocumentSerializer(serializers.ModelSerializer):
...
mysource = MySourceSerializer(many=True) #this one its calling the MysorceSerialize, so there are a endless loop recursion
source : Django Rest Framework-Custom relational fields